340 THE CHEMISTRY OF PROLIFERATION 



prevent undue extension of the proliferation of the 

 normal tissue-cells. But supposing for some reason, 

 such as a slight injury, a local cell-death takes place: 

 it would cause increased proliferation of local cells, 

 and so form the basis of a tumour. Once this growth 

 is started, it will go on until, by causing "irritation" 

 or, to be more accurate, extensive cell-death, it may 

 now induce the cell-proliferation of healing round it, 

 and so, by the formation of connective tissue, cause its 

 progress to be arrested by a capsule. A benign tumour 

 is probably due merely to some localised cell-death in 

 the first place, and it is remarkable how frequently 

 there is a history of injury in these cases. But there 

 is also no doubt that the onset of benign growths, and 

 other cell-proliferation too for that matter, must be con- 

 trolled to some extent by nervous influence. Possibly 

 this nervous influence may be actuated by the nervous 

 control over local elimination. Quite recently a paper 

 appeared in The Lancet on a case of bilateral benign 

 tumours; 1 and this can only be due to some central 

 control over the local causes of cell-division. 



Fibroids of the uterus occur only during the years 

 of menstrual activity. During this time the uterus 

 periodically becomes enlarged, followed by reduction in 

 size. This reduction and quiescence must be accom- 

 panied by death of living cells, and presumably it is 

 this death which, if elimination of the products of 

 katabolism is impaired, may lead to excessive pro- 



1 See a paper on Bilateral Tumours by W. Roger Williams in The Lancet, 

 Feb. 12, 1910. 



